reducer.sum.forbid-nulls is available since version 1.0.11.
reducer.sum.forbid-nulls function computes at each tick the sum of the values of Geo Time Series™ which are in the same equivalence class.
It operates on LONG and DOUBLE.
The location and elevation returned are the first one encountered, which may vary depending on the order of the parameters.
It will return null for any tick where one or more GTS have null values.